1. Field of the Invention
The invention relates to aircraft gas turbine engine rim seals and, particularly, for labyrinth seals having rotating elements supported by flanges of adjacent disks sealing against stationary elements.
2. Description of Related Art
A gas turbine engine of the turbofan type generally includes a fan, a core engine, and a low pressure power turbine. The core engine includes a compressor, a combustor and a high pressure turbine in a serial flow relationship. The compressor and high pressure turbine of the core engine are interconnected by a high pressure shaft. The compressor, turbine, and shaft essentially form the high pressure rotor. The compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. The gas stream flows aft and passes through the high pressure turbine, rotatably driving it and the high pressure shaft which, in turn, rotatably drives the compressor.
The gas stream leaving the high pressure turbine is expanded through a second or low pressure turbine. The low pressure turbine rotatably drives the fan via a low pressure shaft, all of which form the low pressure rotor. The low pressure shaft extends through the high pressure rotor.
Some gas turbine engines have low pressure turbines in which the stages include disks that are bolted together by arm flanges at distal ends of arms extending from the disks. Disposed between the arm flanges is a seal flange supporting an annular platform with labyrinth seal teeth extending radially outwardly therefrom. The seal teeth cooperate with a static seal land mounted at a radially inner end of turbine vane assembly forming a labyrinth seal. Labyrinth seals are used to control and prevent leakage flow from a primary hot flowpath through the turbine. However, some leakage does occur, and migrates through the labyrinth seal downstream to lower pressure regions. In the turbine section, this leakage air is made extremely hot by hot gases from the products of combustion, as the primary airflow expands through the turbine towards the exit of the engine. This high temperature air in radially outer rim cavities between the annular platform and the arms is extremely undesirable, having adverse effect on rotating metal disks and other parts of the gas turbine engine. It is highly desirable to provide relatively cooler airflow into the rim cavities surrounding the upper disk regions and labyrinth seal teeth.